Atopic dermatitis is an inflammatory skin disease, which is characterized by severe itching and eczematous skin lesions and mainly affects infants and children. In particular, in chronic instances, atopic dermatitis often recurs in the winter. Such developed atopic dermatitis often progresses to bronchial asthma or allergic rhinitis, and it occasionally recurs in adults. The severe itching afflicting atopic dermatitis patients may cause a reduction in ability to adapt new environments, physical activity and work efficiency, insomnia, and emotional disturbance. Eczematous skin lesions accompanied by pigmentation bring about an ugly appearance, which may hinder normal personal relationships and social activity. Also, dry and irritant-sensitive skin often develops irritant contact dermatitis, which may be a limiting factor in looking for a job. In recent years, the incidence of atopic dermatitis is increasing worldwide, and is also increasing in South Korea along with the rapid increase in allergic diseases. According to a survey conducted by the Korean Academy of Allergy and Respiratory Disease with a total of 43,045 elementary school and junior high school students nationwide in 2000, 24.9% of elementary school students and 12.8% of junior high school students were diagnosed as having atopic dermatitis. In South Korea, the incidence of atopic dermatitis has increased by 50% for the past ten years, this increase rate being much higher among older people. That is, atopic dermatitis was observed at a high incidence of about 17% in adults.
Atopic dermatitis is thought to result from an interaction between genetic, immunological, and environmental factors. The genetic factors include atopy-associated genes, which are mostly immunological genes. The atopy-associated genes identified so far include human leukocyte antigen (HLA) molecules and chromosome 6p, T cell receptor (TCR) and chromosome 7p, IgE high-affinity receptor (FcεRI-β) and chromosome 11q, and IL-4 and chromosome 5q. The environmental factors may be household mites, household dust, fungi, harmful substances, such as formalin and methylbenzene, released from building materials or paint into the air, or chemical substances used as food additives or food itself.
As an environmental factor, Staphylococcus aureus is a secondary cause of the worsening of apotic dermatitis. S. aureus colonization is found in 80-100% of the eczematous lesions of patients with atopic dermatitis. This is much higher than its occurrence at about 5-30% in the healthy skin. S. aureus makes atopic dermatitis skin lesions worse, for example, by increasing impetigo, and spreads to other individuals, thereby making them susceptible to infections leading to atopic dermatitis. There has been evidence supporting the notion that exotoxins produced by S. aureus act as superantigens in the worsening of atopic dermatitis. Such exotoxins include staphylococcal enterotoxins A-D (SEA-D) and toxic shock syndrome toxin-1 (TSST-1), which increase IgE production about eight times.
Atopic dermatitis patients have commonly been treated using antibiotic therapy, antihistamine therapy, steroid therapy, immunological therapy, and the like. Antibiotic therapy is used to block secondary microbial infections with such as S. aureus, as described above. However, antibiotic therapy is problematic because antibiotics are administered unsuitably, and antibiotic-resistant strains of S. aureus have recently tended to increase. Major antibiotic-resistant strains worldwide include methicillin-resistant Staphylococcus aureus (MRSA), and methicillin-resistant-coagulase-negative Staphylococcus aureus (MRCNS). Thus, owing to a worldwide tendency to avoid the abuse of antibiotics, side effects of the antibiotics, and the emergence of resistant strains, there is an urgent need for the development of materials substituting for antibiotics and other drugs.
In addition, a variety of microorganisms, known as intestinal microflora, inhabit the intestine of humans and animals. Some microorganisms, such as lactic acid bacteria, are known to be beneficial to host animals, and other microorganisms, such as E. coli, Salmonella or Staphylococcus, have direct or potential harmful effects on hosts. In humans and animals, increased stress, infection with harmful bacteria and changes in the external environment may destroy the balance of intestinal microflora, leading to the rapid growth of harmful microorganisms. In this case, the health states of host animals are worsened. Such a change in intestinal microflora brings about allergic diseases. As described above, therapy with antibiotic administration for a long period of time imparts antibiotic resistance to the harmful microorganisms, thereby making effective treatment impossible.
As an alternative regimen of such antibiotic therapy, probiotics are currently receiving increasing interest. Probiotics are prepared by isolating beneficial microorganisms inhabiting the intestine of humans or animals and formulating them into a dosage form. Aerobic bacteria, anaerobic bacteria, lactic acid bacteria, and yeasts are used, lactic acid bacteria being mainly used. Lactic acid bacteria have various applications in traditional food fermentation and processing. Lactic acid bacteria have also been known to be safe for a long time, and some strains thereof are listed as “generally recognized as safe (GRAS)” by the American FDA. Thus, probiotics prepared with lactic acid bacteria have various advantages as follows. They do not have side effects caused by the abuse of antibiotics, and maintain stable intestinal flora by inhibiting the abnormal fermentation of harmful intestinal microorganisms. Also, probiotics reduce diseases caused by infection with harmful microorganisms, and prevent or treat allergic diseases by enhancing the immune system. Among lactic acid bacteria, Lactobacillus species, which are lactobacilli carrying out homolactic or heterolactic fermentation, are naturally found in the intestinal tract of animals, including humans, and during the fermentation of dairy products and vegetables. Lactobacillus species create an acidic environment in the intestine, which helps inhibit the proliferation of harmful bacteria, such as E. coli or Clostridium, relieve diarrhea and constipation, and, as well, offer other health benefits, including enhancement of the immune system, vitamin synthesis, protection against cancer, and serum cholesterol level reduction. Acidophillin, produced by lactobacilli, has been found to inhibit the growth of harmful microorganisms, such as Shigella, Salmonella, Staphylococcus, and E. coli. Also, acidophillin functions to stop diarrhea by inhibiting the proliferation of diarrhea-causing bacteria and normalizing intestinal flora.
Recently, research has been actively conducted to develop probiotics and animal feed using the aforementioned features of Lactobacillus species. Bacterial diarrhea causes reduced body weight gain and death of domestic and farm animals. To prevent the bacterial diarrhea and increase the productivity of farm animals, animal feed has been typically supplemented with antibiotic substances. However, due to the emergence of antibiotic-resistant bacteria and residual antibiotics in livestock products, current regulations in many countries restrict the use of antibiotics in animal feed, and organic feeding programs have been emphasized. At present, the use of probiotics as a substitute method for the use of antibiotics is strongly recommended. European Pat. No. 0861905 discloses a novel Lactobacillus sp. strain, and a pharmaceutical composition and a dairy product for treating gastrointestinal disorders, comprising the novel strain. International Pat. Publication No. WO99/29833 discloses Lactobacillus paracasei, which is a bacterial strain useful as probiotics in food and naturopathic medicines. Korean Pat. Laid-open Publication No. 1998-78353 discloses a novel acid-tolerant microorganism belonging to the genus Lactobacillus, having inhibitory activity on harmful microorganisms, and a probiotic for livestock comprising the novel microorganism.